The present disclosure herein relates to an apparatus for optical emission spectroscopy, and more particularly, to an apparatus for optical emission spectroscopy that measures a plasma state within a plasma process chamber.
In terms of the miniaturization and the advancement of processes for manufacturing semiconductor devices and flat panel display devices, plasma substrate processing apparatuses are being used as apparatuses for performing an etching process, a chemical vapor deposition process, and the like. Such a plasma substrate processing apparatus, high-frequency energy is applied to a stage or electrode to form electric fields or magnetic fields within a plasma processing chamber and then generate plasma by the electromagnetic fields, thereby processing a substrate.
Plasma characteristics such as electron density and ion density within the chamber may be factors that have an influence on a process rate, homogeneity, uniformity, and wafer-to-wafer repeatability in the plasma processing process. For example, the electron density within the plasma processing chamber may have an influence on degrees of excitation, ionization, and dissociation. Thus, to effectively perform the plasma substrate processing process, it may be important to monitor a state within the plasma processing chamber and grasp a plasma state.
A method for obtaining characteristic variables with respect to the plasma state includes a method for measuring plasma density by using a plasma concentration measuring sensor, e.g., a Langmuir probe. In the method for measuring the plasma characteristics by using the Langmuir probe, a metal probe is inserted into the chamber in which a plasma atmosphere is formed, and power is applied to the metal probe to measure a change in current, thereby determining electron density due to the plasma.
In the contact-type measuring method, it may be difficult to measure the characteristics such as the plasma density in real time by inserting the metal probe into the chamber as needed. In addition, since the Langmuir probe directly contact the plasma within the chamber to analyze the plasma state, the Langmuir probe may be contaminated or damaged according to the plasma atmosphere, and also, when the Langmuir probe is introduced into the chamber, foreign substances may be introduced into the chamber.
FIG. 1 is a schematic view of an apparatus for optical emission spectroscopy, which is installed in a plasma process chamber 11 according to the related art, and FIG. 2 is a schematic plan view of the apparatus for the optical emission spectroscopy, which is installed in the plasma process chamber 11 according to the related art. Referring to FIGS. 1 and 2, an optical fiber 14 for the optical emission spectroscopy (OES) that is a technology for optically diagnosing a semiconductor plasma process is limited to an angle of about 30° to about 40° in light incident angle range A. Thus, in case of a wafer W having a size of about 12 inches, the plasma state may be measured on only an area corresponding to about 40% of an entire area of the wafer W. That is, the existing OES technology may have a limitation in that only a portion of the plasma that has an influence on the wafer W, but the whole plasma, is measured.